Methods and apparatus to detect an internally generated signal mode of a local media playback device

ABSTRACT

Methods and apparatus to detect an internally generated signal mode of a local media playback device are disclosed. A disclosed method comprises tuning a harmonic frequency of a chrominance signal output by a local media playback device, and determining that the local media playback device is in an internally generated signal mode if the measured harmonic frequency exceeds a predetermined threshold.

RELATED APPLICATIONS

This patent arises from a continuation of U.S. patent application Ser.No. 11/466,684, now U.S. Pat. No. ______, which is a continuation ofInternational Patent Application Serial No. PCT/US2004/005304, both ofwhich are hereby incorporated by reference in their entireties.

FIELD OF THE DISCLOSURE

This disclosure relates generally to audience measurement, and, moreparticularly, to methods and apparatus to detect an internally generatedsignal mode of a local media playback device.

BACKGROUND

Companies that rely on broadcast video and/or audio programs forrevenue, such as advertisers, television networks and content providers,wish to know the size and demographic composition of the audience(s)that consume their program(s). Audience measurement companies typicallyaddress this need by measuring the demographic composition of a set ofstatistically selected households and the program consumption habits ofthe member(s) of those households. For example, audience measurementcompanies may collect viewing data on a selected household by monitoringthe content displayed on that household's television(s) and byidentifying which household member(s) are watching that content.

Gathering this audience measurement data has become more difficult aslocal media playback devices (such as video cassette recorders, digitalvideo recorders, and personal video recorders) have made time shiftedviewing of broadcast and other programs possible. For example, prior tothe advent of these local media playback devices, televisions were usedsolely to view tuned broadcast programs. As such, an audiencemeasurement company could monitor all of the television viewing bymonitoring the channel to which the television was tuned. However, whena local media playback device is employed, the tuned channel of thetelevision may not be indicative of the program being viewed by theaudience. For instance, a television tuned to a particular channel(e.g., 3 or 4) may not be displaying a program it has tuned, but mayinstead be displaying a program tuned by the local media playback deviceon a completely difference channel, a recorded program played from atape, a digital versatile disk (DVD) or hard disk drive, or a programplayed from another source. Thus, the presence of a local media playbackdevice complicates the audience monitoring process.

A number of different techniques have been proposed for performingaudience measurement in the presence of these local media playbackdevices. Some of these methods seek to detect the presence of bluescreen signals which are internally generated by the local mediaplayback devices in an effort to determine the source of the programmingdisplayed on a television at a given time. As used herein, a blue screensignal is any signal generated by a local media playback device which,when supplied to a television, causes the television to display a bluebackground. A blue screen signal may or may not include information thatcauses a graphic foreground to be displayed against the blue background.

Local media playback devices generate blue screen signals in a varietyof instances. For example, blue screen signals may be displayed: (a)when the local media playback device is displaying a menu to the user orotherwise receiving inputs from a user, (b) during the period beforeand/or after the local media playback device supplies recorded videosignals to a television, (c) when the device is initially powered on andthe user has not yet selected a mode of operation, and (d) when aselected source is not providing an input video signal.

An example local media playback device, (in this instance, a videcassette recorder (VCR)), is shown in FIG. 1. In the illustratedexample, the VCR has two input ports, namely, an antenna in port 2 andan audio/video (a/v) line in port 4. The antenna in port 2 is intendedto be coupled to an external antenna and/or to an external tuner such asa television. The a/v line in port 4 is intended to be coupled to othersources such as a camcorder, another VCR, a DVD player, a digital videorecorder (DVR), a video game, or a personal video recorder (PVR). Theillustrated VCR also has two output ports, namely, a radio frequency(RF) output port 6 and an audio/video (a/v) line out port 8, both ofwhich are intended to be coupled to an external display device such as atelevision or to another type of device (e.g., to another VCR). The RFoutput port 6 is coupled to an RF modulator 10 which functions in theconventional manner to modulate input signals to produce RF outputsignals at a predetermined frequency (e.g., at channel 3 or 4).

To enable the VCR to tune to broadcast programs, the illustrated VCR isprovided with a conventional RF tuner 12. The RF tuner 12 is coupled tothe antenna in port 2 to enable attachment of an antenna to the tuner12.

To enable the playback of recorded media, the VCR of FIG. 1 is alsoprovided with a conventional tape playback mechanism 14. This playbackmechanism 14 typically includes a recording mechanism to enablerecordation of programs tuned by the tuner 12 or otherwise input via oneof the input ports 2, 4.

The VCR of FIG. 1 has a number of output modes. For example, it maysimply pass a tuned broadcast program received from an external tunersuch as a television tuner via, for example, the antenna in port 2 tothe RF modulator 10 via the tuner bypass switch 16. Alternatively, themode switch 18 may be activated in response to a user command to deliverthe signal tuned by the internal tuner 12 of the VCR to the output ports6, 8. In other operating modes, the mode switch 22 may respond to a usercommand by coupling the signal generated by the tape playback device 14or a signal input by the a/v line in port 4 to the output ports 6, 8.

The illustrated VCR is further provided with a blue screen signalgenerator 20. The blue screen signal generator 20 may output a blankblue screen and/or a blue screen with text or other characters. Whenappropriate, the VCR control logic (not shown) cause the mode switch 18to couple the signal generated by the blue screen signal generator 20 tothe output ports 6, 8.

Although the presence of a blue screen signal alone does not preciselydefine the operating mode of the local media playback device, it doesindicate that a local media playback device is operational. Therefore,it is desirable to detect the presence of a blue screen signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an example prior art local mediaplayback device, namely, a video cassette recorder.

FIG. 2 is a schematic illustration of an example local media mode meterto detect an internally generated signal mode of a local media playbackdevice shown in an example environment of use.

FIG. 3A is a graph illustrating an example harmonic frequency trail ofthe chrominance signal of a first example VCR and of the chrominancesignal of an example television.

FIG. 3B is a graph illustrating an example harmonic frequency trail ofthe chrominance signal of a second example VCR and of the chrominancesignal of an example television.

FIG. 4 is a schematic illustration of the example local media mode meterof FIG. 2.

FIG. 5 is a schematic illustration of the example comparison circuit ofFIG. 4.

FIG. 6 is a circuit diagram illustrating an example implementation ofthe local media mode meter of FIGS. 4 and 5.

FIG. 7 is a flowchart representative of machine readable instructionswhich may be executed by the processor of FIG. 6 to implement the localmedia mode meter of FIGS. 4 and 5.

FIGS. 8A and 8B are a flowchart illustrating an example method ofcalibrating the local media mode meter of FIGS. 4-6 to meter an examplelocal media playback device.

DETAILED DESCRIPTION

FIG. 2 is a schematic illustration of an example system to developaudience measurement statistics. In the illustrated example, a centraldata collection office 22 is connected to a plurality of statisticallyselected households 26, 28 via a network 30. The monitored home sites26, 28 are provided with one or more sensors and/or other passive and/oractive data collection engines to gather data identifying the programsconsumed by the members of the monitored households 26, 28, and thehousehold members that consumed those programs. The data collected inthe monitored home sites 26, 28 may be locally stored in an intermediatestorage device 34 such as a hard disk drive. The stored data is exportedperiodically or continuously to the central office 22 via the network30. The data collection office 22 includes one or more computers thatanalyze the data received from the monitored home sites 26, 28 todevelop meaningful audience measurement statistics such as, for example,television ratings, audience share measurements, etc. The network 30 canbe implemented by any desired network such as, for example, theInternet, the public switched telephone network, a wireless connection,dedicated connections, etc.

In the illustrated example, the home sites 26, 28 receive video and/oraudio programs broadcast from one or more broadcasting systems 34.Although FIG. 2 schematically illustrates the broadcasting systems 34 bya radio tower, persons of ordinary skill in the art will readilyappreciate that the broadcasting systems may be implemented by one ormore of a terrestrial broadcasting system, a cable broadcasting system,a satellite broadcasting system, the Internet, or any other broadcastingsystem.

The broadcast programs may include primary content (e.g., entertainment,informational and/or educational content such as movies, televisionnetwork programs, sporting events, news, etc.) and may also includesecondary content (e.g., commercials) interspersed within the primarycontent. For simplicity of discussion, in the following it will beassumed that the broadcast program contains a television program (i.e.,primary content) interspersed with commercials (i.e., secondary content)advertising products of a sponsor of the television program.

The home sites 26, 28 may include any number of information presentingdevices 36 such as a television, a computer, a radio, a stereo, anInternet appliance, etc. The home sites 26, 28 may also include one ormore local media playback devices 40 such as an analog recording device(e.g., a video cassette recorder (VCR)), a digital recording device suchas a digital video recorder, a personal video recorder, a computer, etc,and/or an analog or digital playback device such as a set top box, a DVDplayer, a video game, etc. Each of the home sites 26, 28 includes alocal media mode meter 42 which is coupled to the local media playbackdevice 40 to detect an internally generated signal mode (e.g., a bluescreen generation mode) of the local media playback device 40. The localmedia mode meter 42 cooperates with one or more other sensors and/orother passive and/or active data collection engines to collect audiencemeasurement data regarding the use of the local media playback device.Because the structure and operation of the other data collection enginesare not germane to the present disclosure, they are not discussed infurther detail here. However, persons of ordinary skill in the art whichmay be interested in the types of data collection engines that may beused with the meter 42 are referred to PCT application serial no.PCT/US03/04030, which is hereby incorporated by reference, for adiscussion of some example data collection engines.

As mentioned above, the data collected and/or analyzed by the localmedia mode meter 42 and/or the other data collection engines (not shown)may be periodically exported to the central office 22 via the network 30for further analysis and/or distribution.

The local media mode meter 42 is structured to detect when the localmedia playback device 40 enters a mode wherein it is outputting aninternally generated signal. In the illustrated example, the internallygenerated signal is a blue screen signal which may or may not be outputwith overlying text or other characters (e.g., a menu). To this end, thelocal media mode meter 42 receives a signal output by the local mediaplayback device 40 and attempts to detect a characteristic unique to alocally generated blue screen signal in the received signal. Asexplained in detail below, the characteristic the local media mode meter42 of the illustrated example attempts to detect is in an out-of-bandportion of the chrominance signal received from the local media playback device 40.

By way of background, it is known to persons of ordinary skill in theart that NTSC broadcast signals include a chrominance signal having afundamental frequency of 3.5795 MHz. The bandwidth of a tuned broadcastsignal under the NTSC standard is 4.5 MHz. However, the typical NTSCbroadcast signal will exhibit harmonics to the chrominance signal atfrequencies much higher than the video bandwidth. These harmonics areattenuated. For example, the signal strengths of the harmonics of abroadcast chrominance signal are typically 30 to 50 dB below the signalstrength of the fundamental frequency of the broadcast chrominancesignal.

The inventor of the present invention has discovered that the bluescreen signals output by local media playback devices also exhibit atrail of harmonic frequencies to the fundamental chrominance frequencyof the internally generated blue screen signal. However, to reduce thecosts of the local media playback devices 40, the local media playbackdevices 40 are not provided with expensive circuitry to suppress theseharmonic frequencies. In contrast, to avoid interference with signalsbroadcast in adjacent frequencies, broadcast signals are processed tosuppress the strength of harmonic signals that are outside the videobandwidth of the broadcast signal. As a result, the trail of harmonicfrequencies of a chrominance signal that is internally generated by alocal media playback device 40 (e.g., the chrominance signal of a bluescreen signal) includes harmonics with significantly higher signalstrengths than the corresponding frequencies in a broadcast signal.Specifically, the blue screen signals generated by local media playbackdevices include harmonic frequencies that are 10 to 30 dB higher thanthe corresponding harmonics of a broadcast signal.

FIGS. 3A and 3B illustrate this point. FIG. 3A is a graph illustratingan example harmonic frequency trail 43 of the chrominance signal of afirst example VCR and of an example harmonic frequency trail 44 of thechrominance signal of an example television. FIG. 3B is a graphillustrating an example harmonic frequency trail 46 of the chrominancesignal of a second example VCR and an example harmonic frequency trail44 of the chrominance signal of the same example television. As shown inthose graphs, the harmonic trails of the chrominance signals that areinternally generated by the VCRs include several peaks where the signalstrength is significantly higher than the signal strength of thecorresponding portion of the harmonic trail of the broadcast chrominancesignal. Experiments have shown that known VCRs that are presentlycommercially available in the United States exhibit at least three suchpeaks in the harmonic frequency trails of the chrominance signals fortheir internally generated blue screen signals. Tests have also shownthat these peaks frequently occur between the fifth and the thirteenthharmonic frequencies. In some tested VCRs, the fifth, seventh andeleventh harmonic frequencies are particularly large relative to thesame frequencies in the harmonic trail of a broadcast NTSC signal.

The local media mode meter 42 takes advantage of this difference bytuning one or more of the harmonic frequencies expected for the bluescreen signal of the particular model of local media playback device 40being monitored and comparing the tuned frequenc(ies) to correspondingthresholds. When the tuned frequenc(ies) exceed their correspondingthreshold(s), the local media mode meter 42 concludes that the localmedia playback device 40 is in an internally generated signal mode(e.g., that a blue screen signal is being generated). As a result, thelocal media mode meter 42 creates and stores a time-stamped recordindicating that the monitored local media playback device 40 was in alocally generated signal mode at the detected time.

An example local media mode meter 42 is shown in FIG. 4. In the exampleof FIG. 4, the primary components of the meter 42 are an RF tuner 50 totune a signal output by the local media playback device 40 and acomparison circuit 52 to attempt to detect a characteristic unique to ablue screen video signal in an out-of-band portion of the signal outputby the local media playback device 40 (i.e., in the portion of thesignal tuned by the tuner 50). Additional components of the local mediamode meter 42 include a conventional buffer 54 to tap into the signaloutput by the local media playback device 40 and an analog-to-digitalconverter 56 to convert the analog signal tuned by the tuner 50 into adigital signal for processing by the comparison circuit 52. Of course,if the comparison circuit 52 is able to process analog signals, theanalog-to-digital converter 56 may be eliminated.

In the illustrated example, the tuner 50 is provided with a frequencyselect circuit 58 and a signal level measuring circuit 60. As shown inFIG. 4, the frequency select circuit 58 is responsive to control signalsfrom the comparison circuit 52 to select the frequency tuned by thetuner 50. The tuner 50 tunes to a harmonic frequency (chosen by thecomparison circuit) in the out-of-band portion of the signal output bythe local media playback device 40.

The signal level measuring circuit 60 develops a signal indicative ofthe magnitude of the signal output by the local media playback device 40at the harmonic frequency specified by the frequency select circuit 58.After being digitized by the analog-to-digital converter, the tunedharmonic frequency is passed from the tuner 50 to the comparison circuit52. The comparison circuit 52 compares the magnitude of the tunedharmonic frequency to a threshold selected for the correspondingharmonic frequency (i.e., a threshold that a locally generated bluescreen signal will exceed at the corresponding frequency, but whichordinarily will not be exceeded by a broadcast signal at the samefrequency). If the threshold is exceeded, then the comparison circuit 52drives the frequency select circuit 58 to cause the tuner 50 to tune toanother harmonic frequency in the signal output by the local mediaplayback device 40. The signal level measuring circuit 60 responds byoutputting a signal representative of the magnitude of the newly tunedharmonic frequency. The comparison circuit 52 then compares themagnitude of this new frequency to a threshold appropriate for the tunedfrequency (i.e., a threshold that a locally generated blue screen signalwill exceed, but a broadcast signal will not exceed at the correspondingfrequency). Typically, the thresholds for different harmonic frequencieswill be different from one another, since different signal strengthswill typically be expected at different harmonic frequencies as shown inFIGS. 3A and 3B. However, two or more of the thresholds may possibly besubstantially identical.

As explained above, the illustrated tuner 50 and comparison circuit 52cooperate to sequentially tune to predetermined ones (e.g., first,second, and third ones) of the harmonic frequencies of the chrominancesignal output by the local media playback device 40. The predeterminedfrequencies are selected to correspond to harmonic frequencies thatexhibit peaks when the local media playback device 40 is outputting ablue screen signal. For example, the illustrated tuner 50 maysequentially tune the fifth, seventh and eleventh harmonic frequenciesof the chrominance signal output by the local media playback device 40if an internally generated signal output by the local media playbackdevice 40 exhibits large differences from a broadcast signal at thoseharmonic frequencies.

If each of the measured harmonic frequencies exceeds its correspondingthreshold, the comparison circuit determines that the signal output bythe local media playback device 40 is an internally generated signal(e.g., a blue screen signal). As a result, the local media mode meter 42stores a time-stamped record indicating that the local media playbackdevice 40 was in an internally generated signal mode at thecorresponding time and date.

Although, in the example given above, the local media mode meter 42 onlyidentifies the local media playback device 40 as being in a locallygenerated signal mode (e.g., a blue screen mode) if all of thethresholds are exceeded, persons of ordinary skill in the art willreadily appreciate that less stringent standards might also beappropriate. For example, it might be appropriate to declare the localmedia playback device 40 to be in a locally generated signal mode if themeter 42 determines that less than all of the tested harmonicfrequencies exceed their corresponding thresholds (e.g., two out ofthree frequencies exceed their thresholds). Also, although the aboveexample tests the strength of three harmonic frequencies, other numbersof frequencies (e.g., one, two, four, etc.) may alternatively be tested.

An example comparison circuit 52 is shown in greater detail in FIG. 5.In the example of FIG. 5, the comparison circuit 52 includes a levelcomparator 64 to compare the magnitude of the tuned harmonic frequencyto the corresponding threshold. The thresholds employed by the levelcomparator 64 may be stored in a look-up table 66. The look-up table 66may include, for example, the harmonic frequencies and the correspondingthresholds to be used in testing those frequencies for one or moremodels of local media playback devices 40. Alternatively, the thresholdsmay be determined in a calibration process as explained below inconnection with FIGS. 8A-8B.

The illustrated comparison circuit 52 is further provided with a controlcircuit 68. The control circuit 68 outputs a signal indicative of thenext frequency to be tuned to the frequency select circuit 58. As notedabove, the frequencies to be tuned may be specified in the look-up table66 or stored in a memory 72 as a result of a calibration process, so thecontrol circuit may simply select and output the correct frequency fromthe table 66 or the memory 72. Further, when the level comparator 64 hasexamined all of the harmonic frequencies to be tested and found that themagnitude of each of those frequencies exceeds its correspondingthreshold, the control circuit 68 cooperates with a clock 70 to create atime-stamped record indicating that the local media playback device 40was in an internally generated signal mode (e.g., a blue screen mode) atthe corresponding time. The time-stamped record is written to the memory72 and may be subsequently exported to a central office 24 as explainedabove.

A preferred manner of implementing the local media mode meter 42 isshown in FIG. 6. In the example of FIG. 6, the signal level measuringcircuit 60 is implemented by a low noise amplifier 80, an intermediatefrequency detector 82, and a received signal strength indicator andfilter 84. The frequency select circuit 58 of FIG. 6 is implemented by avoltage controlled oscillator 86 and a phase locked loop 88. Theanalog-to-digital converter 56 and the comparison circuit 52 of FIG. 6are implemented by a processor 90 with analog-to-digital converterinputs. In a preferred implementation, the amplifier 80 is implementedby the amplifier sold by Phillips Electronics under part number BGA2001,the IF detector 82 is implemented by the mixer/IF amplifier sold byPhillips Electronics under part number SA676, the RSSI buffer and filteris implemented by the operational amplifier sold by Analog Devices underpart number OP275, the VCO 86 is implemented by the RF amplifier sold byPhillips Electronics under part number BFG67 and the tuning diode soldby Toshiba under part number 1SV324, the phase locked loop 88 isimplemented by the phase locked loop synthesizer sold by NationalSemiconductor under part number LMX2306, and the processor 90 isimplemented by the microcontroller with A/D inputs sold by Microchipunder part number PIC 18F448.

A flowchart representative of example machine readable instructionswhich may be executed by the processor 90 to implement the local mediamode meter 42 of FIGS. 4-6 is shown in FIG. 7. In this example, themachine readable instructions comprise a program for execution by theprocessor 90. The program may be embodied in software stored on atangible medium such as a CD-ROM, a floppy disk, a hard drive, a digitalversatile disk (DVD), or a memory associated with the processor 90, butpersons of ordinary skill in the art will readily appreciate that theentire program and/or parts thereof could alternatively be executed by adevice other than the processor 90 and/or embodied in firmware ordedicated hardware in a well known manner. Further, although the exampleprogram is described with reference to the flowchart illustrated in FIG.7, persons of ordinary skill in the art will readily appreciate thatmany other methods of implementing the example local media mode meter 42may alternatively be used. For example, the order of execution of theblocks may be changed, and/or some of the blocks described may bechanged, eliminated, or combined.

The program of FIG. 7 begins when a user identifies the model or type oflocal media playback device 40 to be monitored (block 100). As mentionedabove, different models of local media playback devices (e.g., differentmodels of VCRs) typically exhibit different trails of harmonicfrequencies (compare FIGS. 3A and 3B). As such, the harmonic frequenciesto test and the thresholds to use for those frequencies will typicallydiffer from model to model.

After the model number is entered (block 100), the processor retrievesthe frequencies and threshold for the particular model from, forexample, the look-up table 66 (block 102). (If a calibration processsuch as that explained below in connection with FIGS. 8A-8B is employed,block 100 may be eliminated and replaced with the process of FIGS.8A-8B).

Irrespective of how the thresholds are identified, the processor 90outputs the first harmonic frequency to test to the VCO and buffer 86.After a delay sufficient to permit the feedback loop containing the VCO86 and the phase locked loop 88 to stabilize, the processor 90 causesthe IF detector 82 to pass the tuned harmonic frequency to the RSSIbuffer and filter 84 (block 104). The output of the RSSI buffer andfilter 84 is an analog signal representative of the magnitude of theoutput of the local media playback device 40 at the tuned harmonicfrequency. The output of the RSSI buffer and filter 84 is, thus, inputto the processor 90 where it is digitized and compared to the thresholdassociated with the tuned harmonic frequency (block 106).

If the magnitude of the tuned harmonic frequency does not exceed thethreshold (block 106), the local media playback device 40 is not in aninternally generated signal mode (e.g., is not outputting a blue screensignal) and control returns to block 104. Otherwise, the local mediaplayback device 40 may be in an internally generated signal mode (e.g.,outputting a blue screen signal) and control advances to block 108.

At block 108 the processor 90 outputs the second harmonic frequency totest to the VCO and buffer 86. After a delay sufficient to permit thefeedback loop containing the VCO 86 and the phase locked loop 88 tostabilize, the processor 90 causes the IF detector 82 to pass the secondtuned harmonic frequency to the RSSI buffer and filter 84 (block 108).The output of the RSSI buffer and filter 84 is, thus, input to theprocessor 90 where it is digitized and compared to the thresholdassociated with the second tuned harmonic frequency (block 110).

If the magnitude of the second tuned harmonic frequency does not exceedthe threshold (block 110), the local media playback device 40 is not inan internally generated signal mode (e.g., is not outputting a bluescreen signal) and control returns to block 104. Otherwise, the localmedia playback device 40 may be in an internally generated signal mode(e.g., outputting a blue screen signal) and control advances to block112.

At block 112 the processor 90 outputs the third harmonic frequency totest to the VCO and buffer 86. After a delay sufficient to permit thefeedback loop containing the VCO 86 and the phase locked loop 88 tostabilize, the processor 90 causes the IF detector 82 to pass the thirdtuned harmonic frequency to the RSSI buffer and filter 84 (block 112).The output of the RSSI buffer and filter 84 is, thus, input to theprocessor 90 where it is digitized and compared to the thresholdassociated with the third tuned harmonic frequency (block 114).

If the magnitude of the third tuned harmonic frequency does not exceedthe threshold (block 114), the local media playback device 40 is not inan internally generated signal mode (e.g., is not outputting a bluescreen signal) and control returns to block 104. Otherwise, the localmedia playback device 40 is in an internally generated signal mode(e.g., outputting a blue screen signal) and control advances to block116.

At block 116, the processor 90 creates and stores a record indicatingthat the local media playback device 40 was in an internally generatedsignal mode (e.g., outputting a blue screen) at the time indicated bythe clock 70. Control then returns to block 104. Control continues toloop through blocks 104-118 until a reset event (e.g., an interrupt toenter a new model type, a power off, etc.) occurs (block 118). After areset event (block 118), control returns to block 100.

Rather then employing a look-up table to set the thresholds and harmonicfrequencies to test, it may be desirable to set the thresholds andselect the harmonic frequencies based on the actual local media playbackdevice 40 that is to be metered. To this end, a process for calibratingthe local media mode meter 42 to the local media playback device 40 isshown in FIGS. 8A and 8B.

The process of FIGS. 8A-8B begins after the local media mode meter 42has been connected to the output of the local media playback device 40.In the following example, the local media mode meter 42 is assumed to bea VCR coupled to a television, but other local media playback devicesand/or media presentation devices may alternatively be employed. Oncethe local media mode meter 42 is attached to the local media playbackdevice 40, the VCR is tuned to a channel and set to output the tunedsignal via the output ports 6, 8 (block 200). The local media mode meter42 then tunes and stores a set of frequencies output by the local mediaplayback device 40 (block 202). The tuned frequencies lie above thevideo bandwidth of the tuned channel and including harmonics of thechrominance signal output by the local media playback device 40.

The VCR is then placed in an internally generated signal mode (e.g., ablue screen mode) (block 204). The local media mode meter 42 then tunesand stores a set of frequencies output by the local media playbackdevice 40 (block 206). The tuned frequencies in the second setpreferably correspond to the tuned frequencies in the first set.

A difference set is then computed by the processor 90 by subtracting thefirst set from the second set (block 208). The processor 90 then selectsthe three harmonic frequencies in the difference set that have thelargest magnitude to be the harmonic frequencies that will be tuned totest the mode of the local media playback device 40 (block 210). Theprocessor 90 then compares the magnitudes of the selected harmonicfrequencies to a threshold to ensure the magnitude difference issufficient to reliably distinguish the internally generated outputsignal (e.g., blue screen signals) from broadcast and other signals(e.g., tape playback, etc.) (block 212). If the differences are notlarge enough (block 212), an error has occurred and the process must beaborted (block 214), another channel is selected (block 215), and theprocess is repeated with the newly selected channel beginning at clock200. If the differences are large enough (block 212), control advancesto block 216.

At block 216, the processor 90 sets the thresholds for each of theharmonic frequencies. The processor 90 may set these thresholds bymultiplying the magnitude of the corresponding harmonic as measured atblock 206 by a fraction less than one (e.g., 50%, 75%). Once thethresholds are calculated and stored (block 218), the local media modemeter 42 is started to begin executing the program of FIG. 7. Controlthen advances to block 220 (FIG. 8B).

At block 220, the VCR is tuned to a channel to test if the local mediamode meter 42 is properly functioning with the newly selected harmonicfrequencies and thresholds. If the local media mode meter 42 indicatesthat the local media playback device 40 is outputting an internallygenerated signal (e.g., a blue screen signal) (block 222), an error hasoccurred (block 224). Accordingly, another channel is selected (block226). Control then returns to block 200 and the calibration process isre-performed. If no error results (block 222), control advances to block228.

At block 228, the VCR is placed into an internally generated signal modesuch as a menu mode. If the local media mode meter 42 does not indicatethat the local media playback device 40 is outputting an internallygenerated signal (e.g., a blue screen signal) (block 230), an error hasoccurred (block 224). Accordingly, another channel is selected (block226). Control then returns to block 200 and the calibration process isre-performed. If no error results (block 230), the installation has beensuccessful (block 232) and the process terminates.

From the foregoing, persons of ordinary skill in the art will appreciatethat the above disclosed methods and apparatus have providednon-invasive techniques to detect when a local media playback device 40such as a VCR is outputting an internally generated signal such as ablue screen signal. The process is “non-invasive” in that there is noneed to open the housing of or tap into the internal circuitry of thelocal media playback device 40. Instead, all the needed data to monitorthe local media playback device 40 may be obtained by connecting to oneor more of the output ports 6, 8.

Although the above described methods and apparatus are particularly wellsuited for detecting internally generated signals output by VCRs,persons of ordinary skill in the art will appreciate that they may alsobe adapted for use with other local media playback devices such as DVDplayers, DVRs, PVRs, video games, and camcorders.

Although certain example methods and apparatus have been describedherein, the scope of coverage of this patent is not limited thereto. Onthe contrary, this patent covers all methods, apparatus and articles ofmanufacture fairly falling within the scope of the appended claimseither literally or under the doctrine of equivalents.

1. An apparatus to detect an internally generated signal mode of a localmedia playback device, the apparatus comprising: a tuner to tune aharmonic frequency of a chrominance signal output by the local mediaplayback device; a comparison circuit to compare the measured harmonicfrequency to a predetermined threshold; and a memory to store a recordindicating that the local media playback device is in the internallygenerated signal mode if the measured harmonic frequency exceeds thepredetermined threshold, wherein the local media playback devicecomprises a video cassette recorder, a digital versatile disk player, adigital video recorder, a personal video recorder, a video game console,or a camcorder.
 2. An apparatus as defined in claim 1 wherein theharmonic frequency is higher than a video bandwidth of a tuned channel.3. An apparatus as defined in claim 1 wherein the harmonic frequencycomprises a fifth to thirteenth harmonic of the chrominance signal. 4.An apparatus as defined in claim 1 wherein the tuner tunes to a firstharmonic frequency of the chrominance signal output by the local mediaplayback device and a second harmonic frequency of the chrominancesignal output by the local media playback device.
 5. An apparatus asdefined in claim 4 wherein the comparison circuit compares the firstmeasured harmonic frequency to a first predetermined threshold and thesecond measured harmonic frequency to a second predetermined threshold.6. An apparatus as defined in claim 4 wherein the tuner tunes to a thirdharmonic frequency of the chrominance signal output by the local mediaplayback device.
 7. An apparatus as defined in claim 6 wherein thecomparison circuit compares the first measured harmonic frequency to afirst predetermined threshold, the second measured harmonic frequency toa second predetermined threshold, and the third measured harmonicfrequency to a third predetermined threshold.
 8. An apparatus as definedin claim 7 wherein the first predetermined threshold, the secondpredetermined threshold, and the third predetermined threshold aredifferent from one another.
 9. An apparatus as defined in claim 7wherein the first harmonic frequency comprises a fifth harmonicfrequency of the chrominance signal, the second harmonic frequencycomprises a seventh harmonic frequency of the chrominance signal, andthe third harmonic frequency comprises an eleventh harmonic frequency ofthe chrominance signal.
 10. An apparatus as defined in claim 1 whereinthe tuner comprises a signal level measuring circuit and a frequencyselect circuit.
 11. An apparatus as defined in claim 10 wherein thesignal level measuring circuit comprises an intermediate frequencydetector and a received signal strength indicator.
 12. An apparatus asdefined in claim 10 wherein the frequency select circuit comprises avoltage controlled oscillator and a phase locked loop.
 13. An apparatusas defined in claim 1 wherein the comparison circuit comprises aprocessor.
 14. An apparatus as defined in claim 1 wherein the comparisoncircuit comprises: a level comparator to compare the tuned harmonicfrequency to the predetermined threshold; and a control circuit tocontrol the tuner.
 15. An apparatus as defined in claim 14 wherein thecomparison circuit further comprises: a look-up table storing dataidentifying harmonic frequencies and predetermined thresholds to be usedfor predetermined models of local media playback devices; and a clock toprovide a time for time stamping the records stored in the memory. 16.An article of manufacture storing machine readable instructions which,when executed, cause a machine to: tune a harmonic frequency of achrominance signal output by the local media playback device; anddetermine that the local media playback device is in the internallygenerated signal mode if the measured harmonic frequency exceeds apredetermined threshold.
 17. An article of manufacture as defined inclaim 16 wherein the harmonic frequency is higher than a video bandwidthof a tuned channel.
 18. An article of manufacture as defined in claim 16wherein the harmonic frequency comprises a fifth to thirteenth harmonicof the chrominance signal.
 19. An article of manufacture as defined inclaim 16 wherein the machine readable instructions cause the machine totune a harmonic frequency by: tuning a first harmonic frequency of thechrominance signal output by the local media playback device; and tuninga second harmonic frequency of the chrominance signal output by thelocal media playback device.
 20. An article of manufacture as defined inclaim 19 wherein the machine readable instructions cause the machine todetermine that the local media playback device is in the internallygenerated signal mode if the first measured harmonic frequency exceeds afirst predetermined threshold and the second measured harmonic frequencyexceeds a second predetermined threshold.
 21. An apparatus to monitoruse of a local media playback device comprising: a tuner to tune asignal output by the local media playback device; a control circuit toattempt to detect a characteristic unique to a blue screen video signalin an out of band portion of the signal output by the local mediaplayback device; and a memory to store a record indicating that thelocal media playback device is in a blue screen mode if the uniquecharacteristic is detected.
 22. An apparatus as defined in claim 21wherein the signal output by the local media player comprises achrominance signal.
 23. An apparatus as defined in claim 21 wherein theunique characteristic comprises a trail of harmonic frequencies having apredetermined characteristic.
 24. An apparatus as defined in claim 23wherein the trail of harmonic frequencies comprise at least someharmonic frequencies of a chrominance signal.
 25. An apparatus asdefined in claim 24 wherein the at least some harmonic frequencies ofthe chrominance signal exceed a video bandwidth of a tuned channel. 26.An apparatus as defined in claim 24 wherein the predeterminedcharacteristic comprises a set of thresholds corresponding to respectiveones of the at least some harmonic frequencies.